To quote "Perl Best Practices" - "Subroutines always receive their arguments in the @_ array. But accessing them via $_[0],$_1, etc. directly is almost always a Very Bad Idea." See page 178

Conway goes on to say "Moreover, it's easy to forget that each element of @_ is an alias for the original argument; that changing $_[0] changes the variable containing that argument."

So please unpack "@_" and "chomp" the copy. Who knows the calling code might need the trailing "$/"!